A marker light or device on a vehicle promotes visibility to the vehicle. The marker light is typically located on the sides of vehicles less than 80 inches wide and on the back and sides of vehicles greater than 80 inches wide.
A Center High Mount Stop Lamp (or Light) (CHMSL) is a central brake lamp (or light) on a vehicle that is typically mounted higher than the left and right brake lamps on the vehicle. The CHMSL (also known as center brake lamp, third brake lamp, eye-level brake lamp, safety brake lamp, high-level brake lamp, Dole light, or Liddy light) is required in some countries.
In the past, one or more marker lights or devices (e.g., located on the back of the vehicle) and a standard stop light (e.g., located near the lower rear end of the vehicle) have been used on various vehicles. The U.S. government, for example, has required that all vehicles under 80 inches wide have a CHMSL. See Title 49 of the Code of Federal Regulations, Chapter V, Section 571.108, which is incorporated by reference. All vehicles 80 inches or more wide do not require a CHMSL, but require three high mount marker lights in the center at the top of the vehicle.
It is desirable to improve the marker lights, CHMSLs, and brake lights that already exist on most vehicles.